Science · Year 4 · Animals, including humans · Summer Term

The Human Digestive System

Follow the incredible journey of food as it travels through your body and learn about the organs that help us get energy from what we eat.

TL;DR:Take your pupils on an incredible journey inside the human body! This topic uncovers the fascinating process of how a simple sandwich is transformed into the fuel we need to live and play.

• National Curriculum Attainment Targets
• National Curriculum for England: Science Year 4: Animals, including humans

About This Topic

This topic aligns with the Year 4 science curriculum in England, specifically the 'Animals, including humans' strand, which requires pupils to describe the simple functions of the basic parts of the digestive system in humans. This unit provides a foundational understanding of human biology, explaining how the body converts food into the energy needed for growth, repair, and daily activities. The journey of food is a tangible and relatable concept for this age group, allowing for engaging, hands-on learning.

The exploration begins in the mouth, moves through the oesophagus to the stomach, and then into the small and large intestines. The focus is on the main function of each organ: mechanical and chemical breakdown, absorption of nutrients, and removal of waste. This topic also offers an excellent opportunity to reinforce learning about healthy eating and the importance of a balanced diet, connecting scientific knowledge to personal health and wellbeing choices. By understanding the 'why' behind eating, pupils can develop a more informed perspective on their own bodies.

Key Questions

1. Explain the journey of a piece of food from the mouth to the large intestine.
2. Identify the main organs involved in digestion and describe their roles.
3. Compare the function of the stomach with the function of the small intestine.

Learning Objectives

• Identify the main organs of the human digestive system, including the mouth, oesophagus, stomach, small intestine, and large intestine.
• Describe the primary function of each main digestive organ.
• Sequence the journey of food as it travels through the digestive system.
• Explain that the body breaks down food to get energy and nutrients.
• Compare the roles of the stomach and the small intestine in digestion.

Key Vocabulary

Digestion	The process of breaking down food into smaller substances that the body can absorb and use for energy.
Oesophagus	The muscular tube that connects the mouth to the stomach.
Stomach	An organ that uses acid and muscular churning to break down food into a liquid paste.
Small Intestine	A long tube where most of the nutrients from food are absorbed into the blood.
Large Intestine	The tube that absorbs water from undigested food and forms waste (poo).
Enzymes	Special chemicals in the body, like in saliva and the stomach, that help to speed up the breakdown of food.

Watch Out for These Misconceptions

Common Misconception

The stomach does all the work of digestion.

What to Teach Instead

Digestion is a long process that starts in the mouth with chewing and saliva. The stomach breaks food down further, but the small intestine is where most of the nutrients are absorbed into the body.

Common Misconception

Food just falls down a tube into your stomach.

What to Teach Instead

The oesophagus is a muscular tube. It pushes food down into the stomach using waves of muscle contractions, a process called peristalsis. This means you can even swallow if you are upside down.

Common Misconception

Stomach acid is the only thing that breaks down food.

What to Teach Instead

The stomach uses both acid and special chemicals called enzymes to break down food. The churning, muscular action of the stomach wall also helps to physically mash the food into a paste.

Active Learning Ideas

Simulation Game

Digestion in a Bag

Pupils model the stomach using a sealable plastic bag. They add a cracker (food), some water (saliva), and a small amount of orange juice (stomach acid), then mash the bag with their hands to simulate mechanical digestion.

20 min·Pairs

Simulation Game

The Human Body Map

In small groups, one pupil lies on a large sheet of paper while others draw their outline. The group then draws and labels the main organs of the digestive system in the correct positions inside the outline.

45 min·Small Groups

Simulation Game

Stringing It All Together

Pupils use a long piece of string (around 7 metres) to represent the length of the small intestine. This provides a powerful visual and kinaesthetic way to understand the scale of the digestive tract inside their bodies.

15 min·Whole Class

Real-World Connections

• Understanding the importance of chewing food thoroughly to help digestion start in the mouth.
• Connecting a balanced diet, rich in fibre, to maintaining a healthy digestive system and preventing constipation.
• Learning why we need to drink plenty of water to help our bodies digest food and absorb nutrients.
• Recognising the link between the food we eat and the energy we have for playing, learning, and growing.
• Discussing food hygiene, such as washing hands before eating, to prevent harmful bacteria from entering the digestive system.

Assessment Ideas

Exit Ticket

Pupils complete an 'exit ticket' where they label a blank diagram of the digestive system or write one sentence describing the function of the stomach.

Peer Assessment

Create a comic strip or a short presentation that tells the story of a piece of food travelling through the digestive system, explaining what happens at each stage.

Quick Check

Pupils use a traffic light system (red, amber, green) to indicate their confidence in naming the digestive organs and describing their functions.

Frequently Asked Questions

Why does my tummy rumble?

That rumbling sound is usually the muscles in your stomach and intestines squeezing to push food, liquid, and gas through your digestive system. It can be louder when you're hungry because there's no food to muffle the sound.

How long does it take to digest a meal?

It varies, but on average it takes about 6 to 8 hours for food to pass through your stomach and small intestine. The entire journey, from eating to getting rid of waste, can take anywhere from 24 to 72 hours.

What is poo actually made of?

Poo, or faeces, is the waste left over after your body has absorbed all the useful nutrients from your food. It's mostly made of water, undigested food (like fibre), bacteria, and old cells from the lining of your intestines.